1. Field of the Invention
The present invention relates to a completion sub-sea test tree particularly, but not exclusively, to provide tubing and annulus isolation in a production well and the invention also relates to a method of rapid disconnection when completing and testing sub-sea production wells.
2. Description of the Relevant Prior Art
The requirement to perform a well test on a sub-sea well before completion and tree installation is becoming increasingly common. At present, this is performed by running a test string, performing the test and then temporarily suspending the well prior to completion. This procedure has a major impact in three principal areas: it increases cost and rig time during running and retrieving the test string; it creates difficulties when retrieving the well in both terms of time and increased costs, and formation damage may be caused during the suspension and re-entry phases. These problems are particularly relevant with batched drill wells and those with EWT potential.
It is desirable to overcome these problems in such a way which allows a well test/clean up to be conducted through a completion via a conventional production tubing hanger to avoid the need to run and pull the test string and the running and pulling of the suspension system, and associated costs and problems.
An object of the present invention is to provide an apparatus which obviates or mitigates at least one of the aforementioned problems.
A further object of the invention is to provide apparatus which provides isolation of the tubing string and allows disconnection from the well in the event of a rig positioning problem.
A further object of the present invention is to provide isolation of the annulus from the main riser without the requirement to close any of the blow-out-preventer (BOP) rams.
A further object of the invention is to provide the ability to orientate the completion sub-sea test tree, and consequently the attached tubing hanger and completion, into a desired position required to receive the production tree and subsequent tie-backs when deployed.